Pressurized detectors substance analyzer

ABSTRACT

An apparatus, system and method to measure the concentration of a constituent element in a gas sample contained in an analyzer. A sample cell has an inlet and an outlet. The inlet is to receive a predetermined mass of a gas sample and the outlet is to couple to a valve. The sample cell is to receive the predetermined mass of the gas sample over a predetermined pressurization period until substantially the entire mass of the gas sample contained in the analyzer is contained within the sample cell. The gas sample is pressurized to a predetermined pressure over the pressurization period. A detector cell is located adjacent to the sample cell. The detector cell is to determine a concentration of a constituent of the pressurized gas sample.

FIELD

Sample analyzers comprising pressurized detectors employed in analyticalinstruments for substance analysis.

BACKGROUND

Chemical sample analyzers may be employed to measure the content of aparticular element or compound (constituent) in a sample (e.g.,specimen). Throughout this description, it will be understood by thoseskilled in the art that the term constituent element may be used torefer to an analyte, element, compound, component and/or any substancein the sample. Some chemical sample analyzers may be adapted to measurethe content of carbon, sulfur, nitrogen, among others, of a sample.Carbon analyzers may be employed to measure the total organic carbon(TOC), the inorganic carbon (IC), the total carbon (TC; TC=TOC+IC),purgeable organic carbon (POC) and/or non-purgeable organic carbon(NPOC) content of the sample. TOC measurement processes may includeoxidizing organic carbon in the sample, detecting and quantifying theoxidized carbon (e.g., CO₂) and presenting the result in units of massof carbon per volume of the sample.

Carbon analyzers are used in a variety of industries to measure, monitorand analyze analytical information relating to the carbon content of agiven sample. Measuring the carbon content in liquids such as drinkingwater, treated or untreated wastewater and ultra pure water forpharmaceutical or clean room applications is a routine way to assess thepurity of the liquid sample. Monitoring the carbon content of wastewateris particularly significant in the chemical, pharmaceutical,semiconductor, food and beverage industries. Other areas that requirecareful monitoring of carbon content include the paint, resin andcoating industries. Carbon analysis also can be essential forascertaining whether drinking water, groundwater, soils and wastewatercomply with government regulations. Carbon analysis also may beperformed to protect process equipment such as boilers, turbines andpurification devices because organic materials such as carbon maycontaminate the process equipment.

Furthermore, there is an increasing interest in measuring, monitoringand analyzing carbon levels in solids or semi-solid specimens such assoils, clays and sediments. Accordingly, these solids or semi-solids canbe measured, monitored and analyzed for carbon content using knownanalyzer accessories.

Nitrogen analyzers may be employed to measure the nitrogen content inthe sample. Nitrogen in a sample may be converted to nitric oxide (NO).The NO is mixed with ozone to form NO₂* (NO₂ in excited state). When theNO₂* returns to its ground state it gives off energy in the form oflight. This process is known as chemiluminescence. The amount of lightgiven off is proportional to the amount of NO in the sample.

Conventional sample analyzers employ a flow-through type detectortechnique to measure the content of a particular constituent in asample. Flow-through technology provides a certain level of sensitivityin the measured content. There is a need for a sample analyzer tomeasure the content of a constituent in a gas sample with increasedsensitivity over the conventional flow-through type detector techniques.

SUMMARY

A beam of radiation having a specific wavelength is directed through apressurized gas sample in a cell. The specific wavelength is absorbed bya constituent of the sample if present. The amount radiation at thespecific wavelength that is absorbed directly correlates to the amountof the constituent present in the cell.

In various embodiments, an apparatus, system and method are provided tomeasure the concentration of a constituent element in a sample. In oneembodiment, the apparatus is to measure the concentration of aconstituent element in a gas sample contained in an analyzer. A samplecell has an inlet and an outlet. The inlet is to receive a predeterminedmass of a gas sample and the outlet is to couple to a valve. The samplecell is to receive the predetermined mass of the gas sample over apredetermined pressurization period until substantially the entire massof the gas sample contained in the analyzer is contained within thesample cell. The gas sample is pressurized to a predetermined pressureover the pressurization period. A detector cell is located adjacent tothe sample cell. The detector cell is to determine a concentration of aconstituent of the pressurized gas sample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a flow diagram of one embodiment of an analyzer.

FIG. 2A illustrates a cross-sectional schematic diagram of oneembodiment of a detector.

FIG. 2B illustrates a cross-sectional schematic diagram of oneembodiment of a detector.

FIG. 2C a schematic diagram of one embodiment of a chemiluminescencedetection system.

FIG. 3 illustrates one embodiment of a method for measuring theconcentration of a constituent in a pressurized gas sample.

FIGS. 4A, B illustrate one embodiment of a total organic TOC/NPOCcontent method employed by the analyzer shown in FIG. 1 to carry out aTOC/NPOC analysis.

FIG. 5 illustrates one embodiment of a TC content method employed by theanalyzer shown in FIG. 1 to measure the TC content of a sample.

FIG. 6 illustrates one embodiment of an IC content method employed bythe analyzer shown in FIG. 1 to measure the IC contents of a sample.

FIG. 7 illustrates one embodiment of a method employed by the analyzershown in FIG. 1 to measure the TOC of a sample by a different procedure.

DESCRIPTION

Various embodiments are disclosed of analytical instruments comprising asample analyzer and pressurized detector employed to monitor, measureand/or analyze an analytical sample for a predetermined substancereferred to as a constituent element. The sample analyzer may beemployed to monitor, measure and/or analyze constituent elements in ananalytical sample. The content of the constituent element may beunknown. In various embodiments the constituent element to be analyzed,monitored or detected may be predetermined. In one embodiment theconstituent element may be carbon, for example. In addition, alsodisclosed is one embodiment of a method for pressurizing a detector inan analytical instrument as the instrument monitors, measures and/oranalyzes the sample for a constituent element. The embodiments, however,are not limited in this context and the embodiments may be readilyadapted for monitoring, measuring and/or analyzing any sample for anypredetermined constituent element, component, substance and/or compoundin an analytical sample.

In one embodiment, a pressurized sample analyzer may be employed tomeasure the CO₂ produced by the oxidation of carbon in a sample. Thepressurized sample analyzer may comprise a pressurized detector adaptedto measure the CO₂ content of a sample. In various embodiments, thepressurized sample analyzer may be adapted to analyze and measure thecontents of a variety of unknown substances or constituent elements inan analytical sample including Organic Carbon (OC), IC, POC, NPOC and/orTC. The pressurized sample analyzer may employ a pressurized detectiontechnique or a static read technique to oxidize and sweep apredetermined (e.g., specific) carbon component (e.g., CO₂ gas compound)with an inert carrier gas such as nitrogen gas, for example, to a sealeddetector where the carbon component is analyzed. Once a suitable,substantial or entire quantity of the carbon component has been sweptfrom the sample into a cell of the detector, the carbon component ispressurized and single or multiple measurements (e.g., readings) aremade to determine the amount of the carbon component contained in thepressurized cell. The single or multiple measurements may be referred toas “static measurements” because a quantity of the sample is trappedunder pressure in the cell during the measurement. These staticmeasurements correlate directly to the concentration of the specificcarbon constituent element contribution in the sample. In thisparticular technique, the same carbon component is contained in thepressurized detector cell simultaneously during the measurement process.This technique provides increased sensitivity in the measurement. Tomake this type of static measurement the detector may be pressurized toa suitable pressure above atmospheric (e.g., ambient) pressure. Thedetector may be pressurized from one atmosphere up to or beyond severalatmospheres (e.g., two or more atmospheres).

Generally two types of carbon constituent elements may be present in agiven sample, OC such as complex hydrocarbons and IC such as carbonate,bicarbonate and dissolved CO₂. The TC content of a sample includes theTOC content plus the total IC content. Represented formulaically:

TC=TOC+IC

Thus, if the TOC is the quantity of interest, it may be obtaineddirectly by measuring the TOC in the sample or by subtracting the totalIC from the TC. Represented formulaically:

TOC=TC−IC

The amount of TOC can alternatively be measured by detecting andrecording the amount of POC plus the amount of NPOC. POCs are volatileand semi-volatile organic materials that have been sparged from thesample. Generally, however, POCs constitute less than 1% of the TC in agiven sample. Represented formulaically:

TOC=POC+NPOC

Carbon analysis may be conducted by oxidizing a carbon containing sampleto water and CO₂. A sample may be oxidized using an oxidation analyzersuch as a wet chemical oxidation analyzer or a combustion oxidationanalyzer, for example.

Wet chemical oxidation analyzer oxidizes a sample by subjecting it to achemical substance such as persulfate while bombarding the sample withultraviolet (UV) radiation. This reaction produces CO₂ gas. As CO₂ gasis produced from this reaction, a stream of inert gas may be employed tosweep the CO₂ gas into a CO₂ detector. Nitrogen may be used as the inertgas. One such wet chemical oxidation analyzer is the Fusion TOC™analyzer available from the present assignee, Teledyne Tekmar Companyout of Cincinnati, Ohio.

A combustion oxidation analyzer subjects the sample to an elevatedtemperature, sometimes as high as about 1000 degrees Celsius to oxidizethe sample. One such combustion analyzer is the Apollo 9000™ CombustionTOC Analyzer also available from the present assignee, Teledyne TekmarCompany. Both the wet chemical oxidation and the combustion oxidationanalytical methods, provide a theoretically complete oxidation of thecarbon in the sample.

Once the carbon in the sample is oxidized to CO₂ gas, the amount ofcarbon constituent element may be detected and measured in a CO₂detector portion of the analytical instrument. One type of CO₂ detectormay be a Non-Dispersive InfraRed detector (NDIR) to measure the CO₂content in a gas sample. An NDIR detector focuses on the absorptionfrequency of carbon and provides a signal proportional to theinstantaneous concentration of carbon in the carrier gas. This outputsignal may be linearized. Discrete samples of the CO₂ gas aretransferred from a UV reactor to the NDIR detector under pressuresexceeding atmospheric pressures. The static trapped and pressurized CO₂gas sample may be subjected to multiple measurements in the NDIRdetector. The NDIR signal is measured and is referred to storedcalibration data so that the concentration of the carbon constituentelement in the sample is calculated to determine the carbonconcentration of the sample in parts-per-million (ppm),parts-per-billion (ppb) or lower. Further description of an NDIRdetector may be found in U.S. Pat. No. 5,835,216 to Koskinen titled“METHOD OF CONTROLLING A SHORT-ETALON FABRY-PEROT INTERFEROMETER USED INAN NDIR MEASUREMENT APPARATUS”, which is incorporated herein byreference.

FIG. 1 illustrates a flow diagram of one embodiment of an analyzer 100.The analyzer 100 may comprise a reactor 119 and a detector 180. Thereactor 119 is coupled to the detector 180. The analyzer 100 includingthe detector 180 may be pressurized. The analyzer 100 may be implementedto analyze dissolved carbon to measure the carbon content of a sample.The analyzer 100 also may comprise a motor-driven syringe pump 102connected to a primary port 104 of a multi-port valve 106.

In one embodiment, the syringe pump 102 may be employed to deliver asample to the analyzer 100. The syringe pump 102 dispenses a sample intothe reactor 119 where dissolved organic elements or compounds areconverted into a gas. In the case where the sample comprises carbon, thesyringe pump 102 dispenses the carbon containing sample into the reactor119 where it is dissolved and converted into gaseous CO₂, for example.The analyzer 100 may comprise a variety of reactors such as wet chemicaloxidation (UV) or combustion oxidation type reactors. The syringe pump102 may be employed to deliver relatively small volumes (e.g., fromabout 1 μl to about 2.5 ml) of the samples of interest as may be neededin certain types of reactors (e.g., combustion reactors). The syringepump 102 may be adapted to deliver relatively high volumes (e.g., fromabout 25 ml to about 10 ml) of the samples of interest as may be neededin UV or UV/persulfate or heated/persulfate type of reactors. UVreaction chambers may accept larger volumes (e.g., up to about 16 ml) ofthe sample of interest and thus permit measurement of lowerconcentrations of dissolved carbon in the sample.

In the illustrated embodiment, the reactor 119 is a UV-reactor 119 andthe syringe pump 102 is capable of delivering fluids to the reactor 119.The syringe pump 102 is a precision measuring instrument that aspiratesand dispenses fluids. A motor (not shown) drives a valve actuator and asyringe plunger to allow the syringe pump 102 to dispense a knownquantity of fluid. The fluid may comprise a sample, reagent, oxidant,acid, rinsing solution and the like.

In one embodiment, the multi-port valve 106 comprises eight ports: A, B,C, D, E, F, G and H, and is operable to fluidically couple the primaryport 104 to any one of the other ports (A-H). The multi-port valve 106may comprise additional or fewer ports without limiting the scope of theanalyzer 100. When the primary port 104 couples to one of the ports A-Hthe rest of the ports A-H are isolated from each other and from theprimary port 104. The multi-port valve 106 can be actuatedpneumatically, electrically or in any suitable manner with bothclockwise and counterclockwise action. As indicated in the illustratedembodiment, the multi-port valve 106 may be an 8-port valve availablefrom Kloehn Co. Ltd., Las Vegas, Nev. Other suitable single port ormulti-port valves may be employed without limiting the scope of theanalyzer 100.

Each port A-H of the multi-port valve 106 has inputs for specific itemsso as to avoid cross-contamination. For example, port A of themulti-port valve 106 may be reserved for acid, whereas port H may bereserved for an oxidant such as persulfate. The ports A-H are describedbelow.

Port D of the multi-port valve 106 couples to a sample inlet 108 over aline 110. The sample inlet 108 receives a sample 112 of interest to beanalyzed. The sample 112 may be provided individually or in anauto-sampler (ASM) that holds many other samples of interest, forexample.

Port C couples to a sparging chamber 114 of an IC sparger 115 over aline 116. In the sparging chamber 114, dissolved IC and POCs can beremoved from the sample by adding acid to the sample and sparging theresulting mixture. The IC sparger 115 may be a glass vessel that holdsthe sample while the instrument purges the IC and POC from the samplewhile preparing the sample for TOC analysis.

Port B couples to a reaction chamber 118 of the reactor 119 over a line120. In one embodiment, the reaction chamber 118 may comprise a UVsource 122 to convert organic carbon in the sample into carbon gas(e.g., gaseous CO₂). A reagent 124 may be provided in the reactionchamber 118 along with the sample to accelerate the reaction. Thereactor 119 may be a glass vessel comprising the UV source 122. Theanalyzer 100 causes both the sample and the reagent 124 to react and,when combined with the UV rays, oxidizes the carbon in the sample.

Port A couples to an acid inlet 126 over a line 128. The acid inlet 126receives acid from a reservoir of acid 130, preferably a 25% solution ofphosphoric acid (H₃PO₄).

Port H couples to the reagent 124 at inlet 132 over a line 136. Thereagent inlet 132 receives a reagent, e.g., an oxidant, from a reservoirof reagent 124, preferably 10% sodium persulfate (Na₂S₂O₈), but 2% or 3%potassium persulfate (K₂S₂O₈) also can be used. The reagent 124preferably also includes about 5% phosphoric acid. The persulfate/acidmixture of the reagent 124 may be used in the reaction chamber 118,whereas the acid 130 by itself may be used in the sparging chamber 114.One purpose for this separation is to maintain good sparging efficiencyin both the sparging chamber 114 and the reaction chamber 118. Unlikethe reaction chamber 118, the sparging chamber 114 does not include a UVsource to break down persulfate. Residual persulfate can cause aprecipitate to slowly build up on surfaces in the chamber, including theglass frit used as a disperser. Such build-up can clog portions of thefrit, gradually degrading sparging efficiency.

Port G couples to a rinse solution 138 at inlet 134 over a line 137. Therinse solution inlet 134 receives the rinse solution 138 such asde-ionized water.

Port F couples to a waste 141 at outlet 140 over a line 142.

Port E as shown is unused.

With the syringe pump 102 and the multi-port valve 106 orientedvertically as shown, it is possible for minute portions (microliterlevels) of liquid residue in the upper ports A, H, B, G to fall into thesyringe pump 102, causing contamination. Therefore, the acid 130,reagent 124 and rinse solution 138 may couple to the adjacent upperports G, H, A because these liquids 130, 124, 138 have low andconsistent carbon concentrations which are measurable. The sample 112,on the other hand, connects to a downward-facing port D to avoid suchcontamination. In the illustrated embodiment, the sparging chamber 114and the UV reaction chamber 118 may couple to the adjacent ports B, Cbetween the sample port D and the ports A, H, G used for the liquids130, 124, 138. This arrangement, coupled with the bidirectionalcapability of the multi-port valve 106, minimizes valve movement duringoperating procedures described below and minimizes contamination. Theembodiments, however, are not limited in this context.

The analyzer 100 also comprises a carrier gas inlet 144 to receive apressure regulated carrier gas source 146 such as nitrogen, for example,or what is known in the art as ultra-zero air. Lines 148 a-e, 152 a-c,154, T-connection 150, electrically controlled on/off valves 156, 158,flow restrictor 160, pressure regulator 162 and mass flow controller 164are connected (or coupled) as shown to permit the carrier gas deliveredby the carrier gas source 146 to be routed to the sparging chamber 114and to a sparge tube 168 of the reaction chamber 118. The sparge tube168 may be made of glass having a standard glass frit (not shown inFIG. 1) affixed at the bottom thereof as is known in the art to dispersethe carrier gas evenly through the sample and avoid channeling. Thepressure regulator 162 may be adjusted to provide, for example, apredetermined flow of about 200 ml/min, for example, through the vent ofthe valve 172. To measure the flow in the analyzer 100, the valve 172 isturned off and the valve 156 is turned on.

A line 170 a carries gasses away from the sparging chamber 114 to anelectrically controlled 3-port valve 172. Likewise, a line 174 a carriesgasses away from the UV chamber 118 to a valve 176 which is similar tothe valve 172. In an “off” state, the valves 172, 176 connect a common“C” port to a normally open “NO” port while a normally closed “NC” portis isolated. In an “on” state, the C port connects to the NC port andthe NO port is isolated. Gas from the sparging chamber 114 can thus bevented via a line 170 b or sent to a CO₂ detector via a line 170 c,depending on the state of the valve 172. In like manner, gas from the UVchamber 118 can be vented over a line 174 b or sent to a CO₂ detectorover a line 174 c. The lines 170 c, 174 c meet at a T-connection 178. Asillustrated, gas flows from the T-connection 178 to a CO₂ detector 180via lines 182 a-d, a mist trap 186, a permeation tube 188 and a scrubber190.

In one embodiment the detector 180 may be a NDIR or other suitable CO₂detector that is capable of being pressurized. In various otherembodiments, the detector 180 may be employed to detect other elementsand/or compounds. For example, the detector 180 may be used to detectcarbon (C), sulfur (S), nitrogen (N) and other constituent elements invarious compounds. The detector 180 may employ various technologies todetect these constituent elements such as chromatography,chemiluminescence, radiated energy (e.g., infra-red or ultravioletabsorption), among others. These constituent elements each absorb aunique spectrum (e.g., radiated energy at a specific wavelength). Theseconstituent elements also may have a unique chromatographic and/orchemiluminescent signature. In the illustrated embodiment, the detector180 is implemented as an NDIR detector. Gas from the detector 180 may bevented through line 182 e and a valve 196. Waste from the mist trap 186may be drained through a line 197 and a valve 198.

In one embodiment, the detector 180 may have a linearized output toprovide a linearized signal indicative of the amount of CO₂ in the gassample over an electrical line 192 to a computer 194 adapted tocommunicate with the analyzer 100. The computer 194 may be a controlleror processor and in one embodiment may be a dedicated controller orprocessor that resides in the analyzer 100. The computer 194 alsocontrols the valves 106, 156, 158, 172, 176, 196, 198 and the syringepump 102 to execute the various methods of operation. The computer 194may be remotely connected to the detector 180 over any suitable wired orwireless network.

The mist trap 186 and the permeation tube 188 form a moisture controlsystem that may be implemented with standard components and function toremove water vapor from the gas stream. Water vapor is undesirablebecause it can interfere with the CO₂ measurement. The mist trap 186removes water vapor by trapping the mist and the permeation tube 188dries the gas prior to its entering the detector 180. Removing watervapor from the CO₂ is a factor in preserving the reliability andsensitivity of the analysis. Condensation removal occurs by way ofmethods and tubing that are well known in the art.

In one embodiment, the scrubber 190 may be implemented as a halogenscrubber to remove chlorine and other halogens from the CO₂ gas beforeit enters the detector 180 as such substances may damage the detector180. The scrubber 190 may comprise a U-shaped tube filled with glass orpyrex wool and tin and copper granules (beads) to capture halogens asthe CO₂ gas flows through these materials. The tin granules may besandwiched between Pyrex brand wool plugs in one arm 191 a of the “U”and a quantity of copper granules sandwiched between like plugs in theother arm 191 b of the “U”. The scrubber 190 removes chlorine from theCO₂ gas stream by reaction with the copper and tin granules. Chlorine isundesirable because it also can interfere with the CO₂ measurement andalso may harm the detector 180. Discoloration of the copper granules,which are disposed upstream of the tin granules, provides an indicationthat the scrubber 190 should be replaced.

Carrier gas also may be supplied to the sparging chamber 114 throughlines 148 a-e, a pressure regulator 162, a flow restrictor 160 and thevalve 156. Carrier gas also may be supplied to the sparging chamber 114through lines 152 a-b, 154, 148 e, a mass flow controller 164 and thevalves 156, 158. Carrier gas also may be supplied to the sparge tube 168of the UV reaction chamber 118 through lines 152 a-c, the mass flowcontroller 164 and the valve 158.

The mass flow controller 164 has an inlet port 165, an outlet port 167,a mass flow sensor (not shown), a pressure transducer (not shown), and aproportional control valve (not shown). The mass flow controller 164 isfitted with a closed loop control system which is given an input signaleither by an operator, an external circuit/computer or the computer 194.The mass flow controller 164 compares the input signal to the value fromthe mass flow sensor and adjusts the proportional valve accordingly toachieve the required flow. The flow rate is specified as a percentage ofits calibrated full scale flow rate and may be supplied to the mass flowcontroller 164 as a voltage, current or other electrical signal. Themass flow controller 164 generally requires the carrier gas from thesource 146 to be within a predetermined pressure range. In oneembodiment, the pressure at the input of the mass flow controller 164 isin the range of about 80-100 psig. The mass flow controller 164 may beused to measure and control the flow of gases in the analyzer 100. Themass flow controller 164 sets the system operating pressure at itsoutlet port 167. The mass flow controller 164 controls the flow throughthe outlet port 167 until the system pressure reaches the set operatingpressure. When the system reaches the operating pressure, the flowthrough the mass flow controller 164 is cut-off and the system pressureis held static. Measurements of the constituent contained in the gassample are performed under static system operating pressure, asdiscussed in more detail below. The mass flow controller 164 may becalibrated to control a specific type of gas, e.g., Nitrogen, at aparticular range of flow rates. The mass flow controller 164 may begiven a set-point from 0 to 100% of its full scale range but maytypically be operated in the 10 to 90% of full scale range where thebest accuracy may be achieved. The mass flow controller 164 thencontrols the flow rate to the given set-point. The mass flow controller164 may be either analog or digital. A digital mass flow controller isusually able to control more than one type of gas whereas an analogcontroller may be limited to the gas for which it was calibrated. Theembodiments, however, are not limited in this context.

The pressure regulator 162 may be employed to control the flow throughthe flow restrictor 160. The pressure regulator 162 may be set manuallyor automatically under the control of the computer 194 or an externalcontroller.

The flowpath of the analyzer 100 is greatly simplified compared toconventional dissolved carbon analyzers, particularly UV-reactor 119type analyzers, by making effective use of the syringe pump 102 and themulti-port valve 106. The single multi-port valve 106, by virtue of itsmultiplicity of ports selectively coupleable to the primary port 104,connects the syringe pump 102 to each of seven different inlets,chambers or outlets. Accordingly, additional valves may not be requiredin the liquid handling path.

The components of the analyzer 100 shown in FIG. 1 may be arranged in oron an analyzer cabinet or other suitable housing. The syringe pump 102,the multi-port valve 106, the sparging chamber 114, the UV chamber 118,the mist trap 186 and the scrubber 190 may be mounted on a front panelof the analyzer cabinet for ease of viewing to verify operation. Thevalves 106, 156, 158, 172, 176, the flow restrictor 160 and theT-connections 150, 178 may be mounted elsewhere in the analyzer cabinet.Each of the lines that interconnect the various components of theanalyzer 100 (i.e., lines 116, 120, 148 a-e, 152 a-c, 170 a-c, 174 a-c,182 a-e, 197) may be a length of flexible tube and may be of Teflonbrand polymer and generally of small size (0.125 or 0.0625 inch outsidediameter [O.D.]).

Embodiments of the analyzer 100, particularly dissolved carbon analyzersemploying UV, UV/persulfate or heated/persulfate oxidation techniquesmay comprise multiple valves, connections and tubing connected togetherin any suitable arrangement to form lines 116, 120, 148 a-e, 152 a-c,170 a-c, 182 a-e and 197. The analyzer 100 may employ different types oftubes for interconnections. The different types of tubes haveappearances that differ from one another. The tubes may be color-codedto signify their function in the flow path. For example, blue tubes maybe used for lines that carry fluids exclusively to or from the UVchamber 118 and red tubes can be used for lines that carry fluidsexclusively to or from the sparging chamber 114. Yellow tubes can thenbe used for all other lines.

FIG. 2A illustrates a cross-sectional schematic diagram of a detector200. The detector 200 is one embodiment of the detector 180. Thedetector 200 comprises a sample cell 206, first and second detectorcells 210, 212 located adjacent to the sample cell 206, and a radiantenergy source 208 optically coupled to the sample cell 206 and to thefirst and second detector cells 210, 212. The detector 200 employsradiant energy such as electromagnetic radiation to measure aconstituent in a gas sample. A beam of radiant energy has a specificwavelength and is directed through a pressurized gas sample in thesample cell 206. The specific wavelength is selected so that it isabsorbed by a constituent of the sample of interest. The amountradiation at the specific wavelength that is absorbed by the constituentdirectly correlates to the amount of the constituent present in thesample cell 206. The constituent may be any desirable element, and thus,the radiant energy source 208 may be selected to output a beam ofradiant energy having a specific wavelength that may be suitablyabsorbed by the constituent of interest. For example, constituents suchas carbon (C), sulfur (S), nitrogen (N), among other constituentelements, each absorb a different specific wavelength. Therefore, tomeasure the amount of a constituent contained in a pressurized gassample, a radiant energy source 208 that emits a suitable specificwavelength should be employed.

The sample cell 206 comprises an inlet 202 coupled to the line 182 d andan outlet 204 coupled to the line 182 e. The sample cell 206 comprisesfirst and second windows 220, 222 suitable to pass the radiant energy.Accordingly, the sample cell 206 is optically coupled to the firstdetector cell 210. The sample cell 206 defines a chamber 228 thereinhaving a predetermined volume, which is suitable to receive a massquantity of a gas sample to be measured under system operating pressureas set and controlled by the mass flow controller 164. In the embodimentillustrated in FIG. 2A, the system operating pressure of the detector200 may be determined by the thickness and/or strength of the first andsecond windows 220, 222 materials. Thus, the first and second windows220, 222 may be formed of a suitable thickness and/or material to enableits operation under various system operating pressures.

The first and second detector cells 210, 212 are located adjacent to thesample cell 206 and are separated by the second window 222. The firstand second detector cells 210, 212 are fluidically coupled. However, thefirst and second detector cells 210, 212 are fluidically isolated fromthe sample cell 206. The first and second detector cells 210, 212 arefilled with a predetermined gaseous quantity of a constituent elementsimilar to the constituent element of interest in the gas sample to bemeasured. For example, if the constituent is carbon, then the first andsecond detector cells 210, 212 may be filled with a gaseous quantity ofcarbon; if the constituent is sulfur, then the first and second detectorcells 210, 212 may be filled with a gaseous quantity of sulfur; if theconstituent is nitrogen, then the first and second detector cells 210,212 may be filled with a gaseous quantity of nitrogen; and so on. A wall230 separates the first and second detector cells 210, 212. A flowsensor 218 is located between the first and second detector cells 210,212 and provides an opening to enable flow of the constituent gascontained therein to occur therebetween as a result of any pressurechanges between the first and second detector cells 210, 212. The rateof flow between the first and second detector cells 210, 212 isproportional to the amount of radiation from the radiant energy source208 that is absorbed by the gaseous constituent in the first detectorcell 210.

A radiant energy source 208 is located adjacent to the first window 220to emit a beam of incident radiation along the direction indicated byarrow 209 on the gas sample in the sample cell 206. The energy passesthrough the first window 220 into the sample cell 208 and through thesecond window 222 into the first detector cell 210. A rotating chopperblade 214 driven by a motor 216 is located in front of the radiantenergy source 208 and interrupts the energy at predetermined regularintervals. The interruption of the energy causes changes in the energyreaching the first detector cell 210. Pulsating the energy causes apulsing of pressure in the first detector cell 210 and creates a flowthrough the flow sensor 218 between the first and second detector cells210, 212 as indicated by arrow 224. The rate of flow through the flowsensor 218 is proportional to the amount of radiation absorbed by theconstituent in the first sample cell 210. The flow sensor 218 emits anelectrical signal proportional to the magnitude of the flow. When thechamber 228 of the sample cell 206 is empty a maximum amount of radiantenergy reaches the first detector cell 210 and a maximum flow accessthrough the flow sensor 218.

To conduct a measurement, the valve 196 is closed in order to receive amass quantity of the gas sample in the chamber 228 of the sample cell206 while the analyzer 100 is being pressurized to the system operatingpressure by the mass flow controller 164. Thus, while the analyzer 100is being pressurized by the mass flow controller 164, the chamber 228 ofthe sample cell 206 fills with the gas sample of interest and over apredetermined period of time, substantially all of the mass of the gassample in the analyzer 100 is contained in the chamber 228 of the samplecell 206. Once the predetermined time has elapsed and the analyzer inunder the set operating pressure, the mass flow controller maintains theanalyzer, including the sample gas contained in the chamber 228 of thesample cell 206 under operating pressure to conduct the measurement.Accordingly, the radiant energy source 208 emits radiant energy at apredefined wavelength which may be selected according to the constituentto be measured. A quantity of the constituent contained in the chamber208 will absorb a portion of the radiated energy proportionally to thequantity or mass of the constituent. The constituent in the gas sampleabsorbs some of the radiant energy that would otherwise pass through tothe first detector cell 210. The pulsating radiant energy that is notabsorbed by the constituent reaches the first detector cell 210 andcauses a pressure difference between the first detector cell 210 (higherpressure) and the second detector cell 212 (lower pressure). Thedifference in pressure causes a change in flow between the first andsecond detector cells 210, 212. The more energy is absorbed by theconstituent, the less energy reaches the first detector cell 210 and,therefore, the lower the flow between the first and second detectorcells 210, 212. The less energy is absorbed by the constituent, the moreenergy reaches the first detector cell 210 and, therefore, the higherthe flow between the first and second detector cells 210, 212.Therefore, the flow rate between the first and second detector cells210, 212 is inversely proportional to the quantity of the constituentelement of interest contained in the pressurized gas sample in thesample cell 206. Accordingly, the change in flow between the first andsecond detector cells 210, 212 correlates to the amount of theconstituent element in the gas sample. After completing a suitablenumber of flow measurements, the pressurized gas sample in the samplecell 206 may be purged through the outlet 204 by opening the valve 196to vent the pressurized gas sample out of the chamber 228. Accordingly,the flow sensor 218 output signal decreases to its previous “emptychamber 228” level. The area defined by the electrical signal output ofthe flow sensor 218 over time is the raw data that may be analyzed todetermine the amount of constituent contained in the pressurized gassample.

It will be appreciated that the radiant energy source 208 may beselected to emit energy of a predetermined wavelength in any portion ofthe electromagnetic spectrum based on the constituent to be analyzed. Inother words, the wavelength of the energy may be selected so as tocoincide with a particular sorption process for a constituent to beanalyzed. The wavelength of the radiant energy may be selected, forexample, from extreme ultraviolet of about 10 nm to far infrared ofabout 1 mm, for example. Furthermore, the sample cell 206 may be adaptedto receive gas samples at various predetermined pressures aboveatmospheric pressure. The gas pressure may be selected according to adesired sensitivity of the measurement, for example, among the selectioncriteria. The embodiments, however, are not limited in this context.

In one embodiment, the detector 200 may be used to measure a massquantity of carbon constituent in a pressurized CO₂ gas sample. Thesample cell 206 is pressurized to the operating pressure by the massflow controller 164. To initiate the measurement, the outlet 204 of thesample cell 206 is closed, e.g., the valve 196 is closed and the samplecell 206 receives pressurized CO₂ gas outflow from the UV reactor 119(FIG. 1) or the IC sparger 115 (FIG. 1) through the gas inlet 202through line 182 d. A check valve 232 may be located at the gas inlet202 to prevent backflow of the pressurized CO₂ from the inlet 202. Thepressurized CO₂ gas may be purged from the detector 200 through theoutlet 204 through line 182 e after the measurement by opening the valve196 to vent. In one embodiment, the radiant energy source 208 is aninfrared energy source to generate a beam of energy in the infraredwavelength along the direction indicated by arrow 209. The beam ofinfrared energy passes through the first window 220 on one end of thesample cell 206 and is incident on the pressurized CO₂ gas sample to bemeasured for carbon constituents. The infrared energy passes through thepressurized CO₂ sample. Some of the infrared energy may be absorbed bythe pressurized CO₂ gas sample and the rest of the infrared energypasses through the second window 222 to the first detector cell 210. Thefirst and second detector cells 210, 212 are sealed from the sample cell206 and are filled with CO₂ gas. The first and second detector cells210, 212 are isolated from the sample cell 206 by the cell window 220.The cell window 220, however, permits the infrared energy beam to passthrough to the first detector cell 210.

The detector 200 operates by emitting a single beam of infrared energythrough a static pressurized CO₂ gas sample contained in the sample cell206. The beam then hits the first detector cell 210 filled with CO₂ gas.The energy beam, however, is interrupted by the rotating chopper 214driven by the motor 216 and results in a pulsed beam of infrared energy.The pulsed beam results in a different amount of energy reaching thefirst detector cell 210, which results in a pulsing of pressure and flowin the direction indicated by the arrow 224 through the mass type flowsensor 218 located between the first and second detector cells 210, 212.The mass flow sensor 218 emits an electrical signal (e.g., millivolts[mV]) that is proportional to the magnitude of the flow therethrough.When no CO₂ is present in the sample cell 206, the maximum amount ofenergy is available to enter the first detector cell 210 and the flowbetween the first and second detector cells 210, 212 is at its maximum.As previously discussed, in the embodiment illustrated in FIG. 2A, thesystem operating pressure of the detector 200 may be determined by thethickness and/or strength of the first and second windows 220, 222materials. Thus, the thickness and/or material of the first and secondwindows 220, 222 may be selected based on the system operating pressure.

If CO₂ is present in the sample cell 206, it absorbs some of theinfrared energy that would otherwise enter the first detector cell 210,thus reducing the pressure in the first detector cell 210. This resultsin a reduction of flow between the first and second detector cells 210,212. When the CO₂ is purged from the sample cell 206, the signalstrength between the first and second detector cells 210, 212 returns toits previous empty sample cell 206 level.

FIG. 2B illustrates a cross-sectional schematic diagram of a detector250. The detector 250 is one embodiment of the detector 180. Thedetector 250 comprises a housing 262, a detector cell 260, and variouscomponents such as a lamp 252 to emit radiant energy 251, a mirror 254to reflect the radiant energy to an IR detector 256. A window 264separates the lamp 252 and the IR detector 256 from the detector cell260. In one embodiment, the window 264 may be a sapphire window. Atemperature sensor 266 is provided to measure the temperature in thedetector cell 260. The detector 250 may be used to measure the amount ofCO₂ in the sample 112 to determine the carbon content in the sample 112.As previously described, the analyzer 100 converts carbon in the sampleto CO₂ gas. The detector 250 may be an NDIR single-beam, dual-wavelengthinfrared detector that uses no moving parts to measure this CO₂. Aspreviously discussed, the measurement of the CO₂ is proportional to thecarbon in the sample 112 introduced into the analyzer 100.

Inside the detector 250, light in the form of infrared energy 251 froman electronically pulsed miniature lamp 252 is reflected from the mirror254 and re-focused back to the IR detector 256. The mirror 254 may begold plated and coated. The IR detector 256 is located behind asilicon-based Fabry-Perot Interferometer 258 (FPI). This miniature FPI258 is electronically tuned so that its measurement wavelength isconverted between the absorption band of the CO₂ gas and a referenceband. When the FPI 258 passband coincides with the absorption wavelengthof the CO₂ gas, the IR detector 256 experiences a decrease in the lighttransmission. The measurement wavelength of the FPI 258 is then changedto the reference band (that has no absorption lines) and the IR detector256 experiences a full light transmission. The degree of lightabsorption in the CO₂ gas, indicated by the ratio of the two absorptionband and reference band signals, is proportional to the CO₂ gasconcentration. CO₂ shows a unique adsorption spectrum when infraredenergy 251 passes through it, allowing the NDIR detector 250 todistinguish it from other gases.

Pressurized detection, or static read, is a technique used forconcentrating substantially all of the CO₂ produced by the oxidation ofthe sample in the analyzer 100 as previously discussed. The techniquecan be used for both qualitative and quantitative analysis. Somepressurization techniques will now be described.

Using conventional NDIR technology, the measurements are performed byoxidation of the specific carbon component by UV/Persulfate oxidation tocreate CO₂, which is swept through an NDIR detector. In this technique,the adsorption of the infrared light is measured over time as the CO₂ isswept through the conventional NDIR detector. The resulting measurementcorrelates to a peak, which can be integrated and correlated to aconcentration.

Employing the detector 250 in a pressurized detection technique, orstatic read, allows for the specific carbon component to be oxidized andthe resultant CO₂ to be swept into the detector 250 at the inlet port182 d using a non-interfering, inert gas, which is metered by the massflow controller 264. The valve 196 located at the outlet port 182 e ofthe detector prevents the escape of any of the CO₂ from the detector250. A single measurement can be made to determine the amount of CO₂ inthe detector cell 260. The reading correlates directly to theconcentration of the carbon contribution from the sample 112.

An inherent advantage of this technique is that all of the CO₂ is in thedetector cell 260 at the same time for the detector 250 measurement.With all of the CO₂ in the detector cell 260, the sensitivity of theanalysis is significantly increased.

Another advantage of this application is that there is one measurementmade that represents the concentration of CO₂ in the detector cell 260versus multiple measurements made in flow-through designs over time thatresult in a peak. Because this technique is a static read, it eliminatesthe inherent error that is associated with time delays betweenmeasurements employed in conventional flow-through technology. Thesetime delays add error to the integration of the CO₂ peak. Theelimination of this error allows for lower detection limits andincreased precision.

The static read of the detector 250 is accomplished by pressurizing thedetector cell 260 with a carrier gas, which contains the CO₂ from theoxidized sample 112. The pressure required for static read is generallybetween 30-60 psig. Although, as previously discussed, other pressuresmay be used, in one embodiment, the detector 250 pressure may be set toabout 50 psig.

FIG. 2C illustrates a schematic diagram of one embodiment of achemiluminescence detection system 270. The chemiluminescence detectionsystem 270 comprises a chemiluminescence detector 274. Chemiluminescencedetector 274 receives a pressurized nitric oxide (NO) gas sample 272.The sample 112 (FIG. 1) may be injected in a combustion furnace wherethe nitrogen (N) in the sample 112 is converted to NO while carbon isconverted to CO₂. A mass flow controller may be employed to pressurizethe NO gas sample 272 in a manner similar to that discussed above withrespect to the analyzer 100 (FIG. 1), the detector 200 (FIG. 2A), andthe detector 250 (FIG. 2B). The carrier gas sweeps the sample gas 272into the non-dispersive infrared detector (NDIR) (e.g., the detectors200, 250) where the concentration of CO₂ in the sample gas 272 ismeasured. The pressurized NO gas sample 272 is then delivered to thechemiluminescence detector 274 via a line 284. Oxygen (O₂) is fed to anozonator 275 via a line 282. The ozonator 275 converts the O₂ into ozone03 and provides it to the chemiluminescence detector 274 via a line 286.Inside the chemiluminescence detector 274, the pressurized NO gas sample272 is mixed with the O₃. This reaction yields an excited nitrogendioxide (NO₂*). When the NO₂* returns to its ground state NO₂, it givesoff the extra energy in the form of light hv. This process is known aschemiluminescence. The light hv given by the chemiluminescence can beutilized for analyzing the NO or NOX concentration within thepressurized gaseous sample 272.

In the NO mode, the chemiluminescent reaction occurs between the O3 andthe NO yielding NO₂* and oxygen. This reaction produces light hv. Theintensity of th light hv is linearly proportional to the mass of thepressurized NO in the reaction chamber 288. A light-detecting device 276(e.g., a photodiode) converts the light signal hv to an electricaloutput signal 280 that allows quantitation. In one embodiment, thelight-detecting device 276 may be a chemiluminescence photodiodedetector (CLD), for example. The amount of light hv detected is directlyproportional to the amount of NO in the gas sample 272. The light hvmeasured with the light-detecting device 276 and associatedamplification electronics 278 produce the electrical output signal 280.The light-detecting device 276 is thermoelectrically cooled andtemperature regulated. Formulaically, the reaction may be expressed as:

NO+O₃→NO₂*

NO₂*→NO₂ +hv

For NO_(X) detection, NO plus NO₂ is determined as discussed above,however, the sample 272 is first routed through a NO₂ to NO converter,which converts the NO₂ in the sample 272 to NO. The resultantchemiluminescent NO—O₃ reaction is then directly proportional to thetotal NO_(X) concentration.

The total N in the sample 112 (FIG. 1) may be measured in combinationwith the TC in the sample 112. For example, catalytic combustion of thesample 112 may be employed to convert all forms of N in the sample 112to NO and C in the sample 112 to CO₂. The concentration of CO₂ contentmay be measured as discussed above with respect to FIGS. 1, 2A, and 2B.The concentration of NO may be determined as discussed with respect toFIG. 2C. The result may be presented in units of mass C and/or N pervolume or mass of sample 112.

Having described the various components of the analyzer 100, theoperation of the analyzer 100 is now described with reference to FIGS. 1and 2A, 2B. The sample 112 is received from a sample vial and sent tothe reactor 119. The reactor 119 comprises a reagent for oxidation of acomponent of the sample 112 to a gas, e.g., carbon to CO₂. The valve 196is closed and CO₂ is sparged from the reactor 119 into the NDIR detector180. The check valve 232 may be located on the inlet 202 of the NDIRdetector 180 to prevent any CO₂ gas from back flowing out of thedetector 180. The mass flow controller 164 is used to move the CO₂ gasfrom the reactor 119 to the detector 180. The mass flow controller 164component allows the analyzer 100 to maintain a constant flow forsparging while being able to measure the exact pressure in the analyzer100.

In one embodiment, the detector 180 may be an NDIR detector to measurethe carbon content in the pressurized CO₂ gas sample when measuring IC,NPOC or TC. A pressurized detection technique (static read) enables themeasurement of the specific carbon constituent contained in the sample112. While the operating pressure is building, the carbon constituentcan be oxidized and swept with an inert carrier gas such as nitrogen gasinto a sealed NDIR cell detector 180 for measurement. Once all of theCO₂ gas has been swept from the sample 112 into the sample cell 206 ofthe detector 180, single or multiple measurements can be made todetermine the amount of carbon constituent contained in the pressurizedCO₂ gas contained in the detector 180. This measurement correlatesdirectly to the concentration of the specific carbon constituent in theoriginal sample 112 received by the analyzer 100.

One advantage of employing the pressurized technique described herein isthat substantially the entire mass of the CO₂ gas is the particularsample being measured may be contained in the detector 180 at the sametime during one or more measurements. Having substantially all of theCO₂ mass in the in the detector 180 at the same time may increase thesensitivity of the analysis. In various embodiments, the sensitivity maybe increased up to approximately 25%. Another advantage of employing thepressurized technique is that the measurement of the concentration ofCO₂ is made on the sample contained in the detector 180. In contrast, inconventional flow-through techniques, there is an inherent error becausemultiple separate measurements are made at separate times while the CO₂gas sample flows through a conventional flow-through type CO₂ detector.These multiple measurements are then integrated to a peak. The staticpressure technique described herein employed in the analyzer 100eliminates the inherent error that is associated with the time delaysbetween the multiple measurements. The delays add error to theintegration of the CO₂ peak. The elimination of this inherent error inthe pressurized analyzer 100 also helps to lower calculated minimumdetection limits (MDL). The technique employed in the pressurizedanalyzer 100 also simplifies the hardware and software requirements toachieve the desired measurements for the CO₂ gas sample to determine thecontent of the carbon constituent in the sample 112.

In order to make a static measurement, the detector 180 is pressurizedto an operating pressure above atmospheric pressure by the mass flowcontroller 164. In various embodiments, the detector 180 may bepressurized to well above atmospheric pressure such as, for example, upto 3 atmospheres above atmospheric pressure. In one embodiment, thedetector 180 may be pressurized up to 2.4 atmospheres above atmosphericpressure. In terms of pounds-per-square-inch (psi), the detector 180 maybe pressurized from 30 psi-60 psi above atmospheric pressure. Forexample, the NDIR sample cell 206 of the detector 180 may be pressurizedfrom atmospheric pressure (e.g., about 14.7 psi) up to about threeatmospheres (e.g., about 60 psi) above atmospheric pressure. In oneembodiment, the detector 180 may be pressurized anywhere fromatmospheric pressure up to about 30 psi above atmospheric pressure. Inanother embodiment, the detector 180 may be pressurized anywhere fromatmospheric pressure up to about 60 psi above atmospheric pressure. Inone example, the NDIR sample cell 206 may be pressurized to about 2.4atmospheres. The mass flow controller 164 may be used to manually orautomatically regulate and/or adjust the operating pressure in thedetector 180 (and/or the analyzer). As previously described, the massflow controller 164 may be used to move substantially the entire mass ofCO₂ gas from the reactor 119 to the detector 180. The mass flowcontroller 164 comprises a pressure transducer to measure the operatingpressure of the analyzer 100. It will be appreciated by those skilled inthe art that the pressurization levels described herein are non-limitingexamples. Any suitable pressure above atmosphere may be employed topressurize the analyzer 100 (e.g., the detector 180) in accordance withthe desired analysis of a particular constituent element in the sample112. The analyzer 100 is pressurized to move substantially the entiremass of the gas sample containing the constituent of interest into thedetector cell 180 for measurement purposes.

Prior to placing the analyzer 100 in an instrument condition ready toreceive the sample 112, the analyzer 100 may execute a cleaningprocedure to clean the sparger 115, the reactor 119 and anyinterconnecting lines. One technique for cleaning a liquid sample carbonanalyzer is described in commonly assigned U.S. Pat. No. 6,007,777 toPurcell et al. titled “LIQUID SAMPLE CARBON ANALYZER”, the entirecontents of which are incorporated herein by reference. Other suitablecleaning techniques may be employed. The methods 400, 500, 600, 700employed by the analyzer 100 to carry out the various analyses discussedbelow may be carried out by the computer 194 or any processor (e.g., amicroprocessor-based controller) coupled to the analyzer 100.

FIG. 3 illustrates one embodiment of a method 300 for measuring theconcentration of a constituent element in a gas sample. In oneembodiment, the outlet of the sample cell 206 of the detector 180 issealed 302. A predetermined volume of a gas sample may be received 304through the inlet 202 into the sample cell 206. The gas sample may bepressurized 306 above atmospheric pressure. And a concentration of aconstituent in the pressurized gas sample may be determined 308.

In one embodiment, the liquid sample 112 may be received in the reactor119 and the liquid sample 112 may be converted into the gas sample to bemeasured. The gas sample may be swept from the reactor 119 to the samplecell 206. A carrier gas may be received into the reactor 119 to sweepthe gas sample from the reactor 119 to the sample cell 206. In thesample cell 206, the gas sample may be pressurized to a pressure aboveatmospheric pressure. The determining of the concentration of theconstituent of the pressurized gas sample while the gas sample is in thesample cell 206 may be repeated multiple times.

In one embodiment, the liquid sample 112 may be received in the spargingchamber 114. The liquid sample 112 to be measured may be sparged with anacid 130 and the gas sample may be swept from the sparging chamber 114to the sample cell 206. In the sample cell 206, the gas sample may bepressurized to a pressure above atmospheric pressure.

In the embodiment of the detector 200 shown in FIG. 2A, a method 300comprises emitting a beam of incident radiation by the radiant energysource 208 along the direction indicated by arrow 209 on the pressurizedgas sample contained in the sample cell 206 and determining theconcentration of the constituent in the pressurized gas samplecorresponding to a quantity of the radiation absorbed by the pressurizedgas sample. The method 300 also may comprise interrupting the beam ofincident radiation at predetermined intervals by a rotating chopper disk214 and measuring a flow rate between a first cell and second detectorcell 210, 212 using a mass flow sensor 218. The first and seconddetector cells 210, 212 are filled with a predetermined quantity of theconstituent element to be measured in the gas sample. The flow rate maybe integrated over time. The concentration of the constituent element inthe pressurized gas sample may be correlated with the integrated flowrate over time.

FIGS. 4A, B illustrate one embodiment of a TOC/NPOC content method 400employed by the analyzer 100 to carry out a TOC/NPOC analysis. It isknown that the TOC of many samples can be ascertained by measuring theNPOC content of such samples. First, acid 130 is added to the sample 112and the resulting mixture is sparged in the sparger 115, thus removingthe IC and POC from the sample 112. Next a persulfate solution oroxidant or other reagent 124 is added to the mixture and the resultingnew mixture is exposed to UV radiation in the reactor 119. NPOC, theonly remaining carbon in the sample 112, is converted to CO₂ gas whichis pressurized above atmospheric pressure and is measured in the samplecell 206 of the detector 180 in accordance with the method 300previously described.

The valves 154, 156, 176, 196 are “off” unless otherwise specified.After a system initialization, the syringe 102 is rinsed 402 one or moretimes using a predetermined volume (e.g., 1 ml) of the sample 112. Thesyringe 102 is loaded with the sample 112 and then discharged to waste141. A predetermined or preprogrammed volume of the sample 112 isdelivered 404 to the sparging chamber 114. The syringe 102 is rinsed 406with water or other rinse solution 138 using the procedure previouslydescribed, and a volume of acid 130 is injected 408 through the line 116to the sparging chamber 114. This technique permits larger volumes ofthe sample 112 to be delivered to the sparging chamber 114, the deliveryof the acid 130 flushes any sample resident in the line 116 into thesparging chamber 114 and ensures complete processing of the programmedvolume of the sample 112. In other embodiments, both the sample 112 andthe acid 130 may be loaded into the syringe 102 and then delivered tothe sparging chamber 114. The acid/sample mixture is sparged 410 for apredetermined or programmed period. Any CO₂ or any other carbon speciesexiting the sparging chamber 114 are released to vent through the line170 b. The syringe 102 is rinsed 412 one or more times with theacid/sample mixture being sequentially loaded and sent to waste 141. Theacid/sample mixture is aspirated 414 into the syringe 102. A volume V₁of the contents of the syringe 102 (acid/sample mixture) are thendelivered 416 to the reaction chamber 118 where it is exposed to UVrays. The syringe 102 is rinsed 418 and control moves to a decisionblock. (Note: V₂ is defined as a previously programmed or defined volumeof the reagent 124 to be mixed with the sample/acid mixture volume V₁.)

The desired reagent 124 volume is added 420 to the syringe 102. Thereagent 124 volume V₂ (and the volume V₃ of the rinse solution, if any)is delivered 422 to the reaction chamber 118. This flushes any sampleresident in the line 120 into the reaction chamber 118 to again ensurecomplete processing of the sample 112. In the reactor 119, the UVradiation from the lamp 122 immediately begins converting organic carbonin the sample 112 to CO₂ gas in the reaction chamber 118. The valves 158and 176 are turned “on” and any CO₂ gas in the reaction chamber 118 isswept 428 by the carrier gas into the detector 180 sample cell 206 undersystem pressure as may be determined, for example, by the pressureregulator 162. As previously discussed, the analyzer 100 may bepressurized 430 from atmospheric pressure (e.g., about 14.7 psi) toabout three atmospheres (e.g., about 60 psi) above atmospheric pressure.The mass flow controller 164 moves or sweeps the CO₂ gas from thereaction chamber 118 to the sample cell 206 of the detector 180. In thesample cell 206, the CO2 gas is maintained, under system pressure beforeand during the measurements. The detector 180 measures 432 the carbonconstituent content in the pressurized CO₂ gas trapped in the samplecell 206 one or multiple times in accordance with the process describedin the method 300. In one embodiment, for example, the detector 180 maybe implemented as a pressurized NDIR1 detector and infrared radiationmay be employed to determine the carbon constituent content in thepressurized CO₂ gas sample trapped in the sample cell 206. The one ormultiple measurements of the same pressurized CO₂ gas sample may berecorded 434 (e.g., stored in memory or storage or may be transmitted orotherwise communicated) by the computer 194. When the one or multiplemeasurements are completed, any remaining contents in the spargingchamber 114 are sent 436 to waste. The sparging chamber 114 is thenrinsed 438 by transferring the now carbon-free contents of the reactionchamber 118 to the sparging chamber 114 and then expelling such contentsto waste 141. The analyzer 100 then returns 440 to its instrument readystate.

It will be noted that the sparging chamber 114 may remain substantiallyidle after a volume V₁ of liquid is transferred to the reaction chamber118. Accordingly, multiple samples 112 may be processed in a shortenedoverall time period. For example, while one sample is being processed inthe reaction chamber 118, the sparging chamber 114 is rinsed and loadedwith the next sample. IC thus may be removed from the subsequent samplein the sparging chamber 114 at the same time OC in the prior sample isbeing converted to CO₂ gas, removed from the reaction chamber 118, anddetected by the detector 180. The time savings realized by thisprocedure may be increased where scores of samples are to be processedin sequence, such as with an autosampler.

FIG. 5 illustrates one embodiment of a TC content method 500 employed bythe analyzer 100 to measure the TC content of a sample 112. In thisprocedure, the acid 130 and the persulfate reagent 124 may be added tothe sample 112 in the reaction chamber 118, where both IC and TOC areconverted to CO₂ gas. The CO₂ gas is swept out of the reaction chamber118 by the carrier gas under system pressure and detected by thedetector 180 in the pressurized sample cell 206.

At initialization, the valves 154, 156, 172, 176, 196 are set to off,on, on, on, off, respectively. This shuts off the carrier gas flow tothe sparging chamber 114, turns on the carrier gas flow to the reactionchamber 118, and routes the CO₂ gas exiting the reaction chamber 118 tothe detector 180 under the system pressure set by the pressure regulator162. As previously discussed, the analyzer 100 may be pressurized from apressure of about one atmosphere (e.g., about 14.7 psi) to about threeatmospheres (e.g., about 60 psi) above atmospheric pressure. The syringe102 is rinsed 502 and the sample 112 is loaded 504 into the syringe 102thereafter. A baseline is monitored 506 and the valve 156 supplyingcarrier gas to the reaction chamber 118 is shut off 508 and then avolume V₁ of the sample 112 is delivered 510 to the reaction chamber118. UV radiation from the lamp 122 immediately begins convertingorganic carbon in the sample 112 to CO₂ gas. The valves 158 and 176 areturned on and any CO₂ gas in the reaction chamber 118 is swept 512 bythe carrier gas into the sample cell 206 of the detector 180 undersystem pressure where the carbon content in the CO₂ gas may be measured514 as previously discussed. The system pressure may be set manually orautomatically by the pressure regulator 162. When the measurements arecompleted, the reaction chamber 118 contents are aspirated to thesyringe 102 pump and then discharged directly to waste 516.

FIG. 6 illustrates one embodiment of an IC content method 600 employedby the analyzer 100 to measure the IC contents of the sample 112. Inthis procedure, the sample 112 is mixed with the acid 130 in thesparging chamber 114. IC in the sample 112 reacts with the acid 130 toform CO₂ gas, which is sparged out of the sample 112 and carried to thedetector 180 under system pressure as previously discussed.

From the ready state the analyzer 100 is initialized. The valves 154,156, 172, 176, 196 are set to off, on, on, on, off, respectively. Thecarrier gas does not flow through reaction chamber 118 but does flowthrough the sparging chamber 114 and from there to the CO₂ detector 180under system pressure as previously discussed. The valve 154 is shut off602, turning off the flow of the carrier gas to the sparging chamber 114to prepare for loading the sample 112. The sample 112 is delivered 604and the syringe 102 is rinsed 606. V₂ is defined as the desired acidvolume. The valve 156 is turned on and the CO₂ gas is swept 608 to thedetector 180 under system pressure as previously discussed. The contentsof carbon in the CO₂ gas is measured 610. When the measurements arecompleted, a value representative of the IC is obtained by the computer194 and stored. The sparging chamber 114 contents are aspirated to thesyringe 102 pump and then discharged directly to waste 612.

FIG. 7 illustrates one embodiment of a method 700 employed by theanalyzer 100 to measure the TOC contents of a sample by a differenceprocedure. The amount of TOC in the sample 112 can be rigorouslymeasured by separately measuring the sample TC and IC as discussedabove. The TOC content of the sample 112 is then calculated as:

TOC=TC−IC.

Measure 702 the TC content in a first aliquot of the sample 112according to the method 500 of FIG. 5, which first aliquot is thendischarged to waste 141. Measure 704 the IC content in a second aliquotof a sample 112 according to the IC content method 600 of FIG. 6.Calculate 706 the difference between the TC and IC values to yield theTOC content of the sample 112. This may be calculated by the computer194.

While certain features of the embodiments have been illustrated asdescribed herein, many modifications, substitutions, changes andequivalents will now occur to those skilled in the art. It is thereforeto be understood that the appended claims are intended to cover all suchmodifications and changes as fall within the true scope of theembodiments.

1. A method for measuring the concentration of a constituent element ina gas sample contained in an analyzer, the method comprising: sealing anoutlet of a sample cell of a detector; receiving a predetermined mass ofa gas sample through an inlet into the sample cell over a predeterminedpressurization period until substantially the entire mass of the gassample contained in the analyzer is contained within the sample cell,wherein the gas sample is pressurized to a predetermined pressure overthe pressurization period; and determining a concentration of aconstituent element in the pressurized gas sample.
 2. The method ofclaim 1, comprising: emitting a beam of incident radiation on thepressurized gas sample in the sample cell.
 3. The method of claim 2,comprising: determining the concentration of the constituent element inthe pressurized gas sample in proportion to a quantity of the radiationabsorbed by the pressurized gas sample.
 4. The method of claim 3,comprising: interrupting the beam of incident radiation at predeterminedintervals; measuring a flow rate between a first detector cell and asecond detector cell, the first and second detector cells are filledwith a predetermined quantity of a constituent element to be measured inthe gas sample; and wherein the concentration of the constituent elementin the pressurized gas sample is proportional to the flow rate betweenthe first and second detector cells integrated over a predeterminedperiod of time.
 5. The method of claim 1, comprising: receiving a liquidsample in a reactor; converting the liquid sample into the gas sample tobe measured; and sweeping the gas sample from the reactor to the samplecell during the pressurization period.
 6. The method of claim 5,comprising: receiving a carrier gas into the reactor to sweep the gassample from the reactor.
 7. The method of claim 1, comprising: repeatingthe determining of the concentration of the constituent element of thepressurized gas sample while the pressurized gas sample is in the samplecell.
 8. The method of claim 1, comprising: pressurizing the gas samplein the sample cell to a pressure above atmospheric pressure.
 9. Themethod of claim 1, comprising: receiving a liquid sample in a spargingchamber; sparging the liquid sample to be measured with an acid; andsweeping the gas sample from the sparging chamber to the sample cell.10. The method of claim 1, comprising: emitting a beam of incidentradiation on the pressurized gas sample in the sample cell; reflectingthe beam of radiation from a mirror; and detecting a quantity ofradiation reflected from the mirror.
 11. The method of claim 11,comprising determining the concentration of the constituent element inthe pressurized gas sample based on the detected reflected quantity ofradiation.
 12. The method of claim 1, comprising: contacting thepressurized gas sample with a second gas sample to produce an excitedstate of a third gas sample; and detecting a quantity of light emittedwithin a period of time during which the excited third gas samplereturns to a ground state from the excited state.
 13. An apparatus, formeasuring the concentration of a constituent element in a gas sample,contained in an analyzer, the apparatus comprising: a sample cell havingan inlet and an outlet, the inlet to receive a predetermined mass of agas sample and the outlet to couple to a valve, the sample cell toreceive the predetermined mass of the gas sample over a predeterminedpressurization period until substantially the entire mass of the gassample contained in the analyzer is contained within the sample cell,wherein the gas sample is pressurized to a predetermined pressure overthe pressurization period; and a detector cell located adjacent to thesample cell, the detector cell to determine a concentration of aconstituent element in the pressurized gas sample.
 14. The apparatus ofclaim 13, comprising: a radiant energy source optically coupled to thesample cell to emit a beam of incident radiation on the pressurized gassample in the sample cell.
 15. The apparatus of claim 14, wherein thedetector cell comprises: a first detector cell; and a second detectorcell fluidically coupled to the first cell; the first and seconddetector cells to develop a flow therebetween that is inverselyproportional to the radiation absorbed by the pressurized gas sample.16. The apparatus of claim 15, comprising: a chopper blade located infront of the radiant energy source to interrupt the beam of incidentradiation at predetermined intervals; a flow sensor located between thefirst and second detector cells to measure a flow rate between the firstdetector cell and the second detector cell, the first and seconddetector cells are filled with a predetermined quantity of theconstituent element to be measured in the pressurized gas sample, theflow sensor to output an electrical signal that is proportional to therate of the flow through the flow sensor; and a processor coupled to theflow sensor to read the electrical signal and integrate the electricalsignal over time; wherein the concentration of the constituent elementin the pressurized gas sample is proportional to the integratedelectrical signal over time.
 17. The apparatus of claim 13, comprising:a reactor coupled to the sample cell, the reactor to receive a liquidsample and to convert the liquid sample into the gas sample to bemeasured; and a mass flow controller coupled to the reactor, the massflow controller to pressurize and sweep the gas sample from the reactorto the sample cell.
 18. The apparatus of claim 17, comprising: a carriergas inlet to couple to a pressure regulated carrier source, the carriergas inlet to receive a carrier gas into the reactor to sweep the gassample from the reactor to the sample cell during the pressurizationperiod.
 19. The apparatus of claim 17, wherein the mass flow controllerpressurizes the gas sample to a pressure above atmospheric pressure. 20.The apparatus of claim 13, comprising: a sparging chamber coupled to thesample cell, the sparging chamber to receive a liquid sample therein andto sparge the liquid sample to be measured with an acid; and a mass flowcontroller coupled to the sparging chamber, the mass flow controller isto pressurize and sweep the gas sample from the sparging chamber to thesample cell.
 21. The apparatus of claim 13, comprising: a radiant energysource to emit a beam of incident radiation on the pressurized gassample in the sample cell; a mirror to reflect the beam of radiation;and a photo-detector to detect a quantity of radiation reflected fromthe mirror.
 22. The apparatus of claim 13, comprising: a reactionchamber to receive the pressurized gas sample and a second gas sample toproduce an excited state of a third gas sample; and light-detectingdevice to detect a quantity of light emitted within a period of timeduring which the excited third gas sample returns to a ground state fromthe excited state.
 23. A system, comprising: a carrier gas source; and asample cell having an inlet and an outlet, the inlet to receive apredetermined mass of a gas sample and the outlet to couple to a valve,the sample cell to receive the predetermined mass of the gas sample overa predetermined pressurization period until substantially the entiremass of the gas sample contained in the analyzer is contained within thesample cell, wherein the gas sample is pressurized to a predeterminedpressure over the pressurization period; and a detector cell locatedadjacent to the sample cell, the detector cell to determine aconcentration of a constituent element in the pressurized gas sample.24. The system of claim 23, comprising a radiant energy source opticallycoupled to the sample cell to emit a beam of incident radiation on thepressurized gas sample in the sample cell.
 25. The system of claim 24,wherein the detector cell comprises: a first detector cell; and a seconddetector cell fluidically coupled to the first cell; the first andsecond detector cells to develop a flow therebetween that is inverselyproportional to the radiation absorbed by the pressurized gas sample.26. The system of claim 25, comprising: a chopper blade located in frontof the radiant energy source to interrupt the beam of incident radiationat predetermined intervals; a flow sensor located between the first andsecond detector cells to measure a flow rate between the first detectorcell and the second detector cell, the first and second detector cellsare filled with a predetermined quantity of the constituent element tobe measured in the pressurized gas sample, the flow sensor to output anelectrical signal that is proportional to the rate of the flow throughthe flow sensor; and a processor coupled to the flow sensor to read theelectrical signal and integrate the electrical signal over time; whereinthe concentration of the constituent element in the pressurized gassample is proportional to the integrated electrical signal over time.27. The system of claim 23, comprising: a reactor coupled to the samplecell, the reactor to receive a liquid sample and to convert the liquidsample into the gas sample to be measured; and a mass flow controllercoupled to the reactor, the mass flow controller to pressurize and sweepthe gas sample from the reactor to the sample cell. a reactor coupled tothe sample cell, the reactor to receive a liquid sample and to convertthe liquid sample into the gas sample to be measured; and a mass flowcontroller coupled to the reactor, the mass flow controller to sweep thegas sample from the reactor to the sample cell.
 28. The system of claim27, comprising: a carrier gas inlet to couple to a pressure regulatedcarrier source, the carrier gas inlet to receive a carrier gas into thereactor to sweep the gas sample from the reactor to the sample cellduring the pressurization period.
 29. The system of claim 27, whereinthe mass flow controller pressurizes the gas sample to a pressure aboveatmospheric pressure.
 30. The system of claim 23, comprising: a spargingchamber coupled to the sample cell, the sparging chamber to receive aliquid sample therein and to sparge the liquid sample to be measuredwith an acid; and a mass flow controller coupled to the spargingchamber, the mass flow controller is to pressurize and sweep the gassample from the sparging chamber to the sample cell.
 31. The system ofclaim 23, comprising: a radiant energy source to emit a beam of incidentradiation on the pressurized gas sample in the sample cell; a mirror toreflect the beam of radiation; and a photo-detector to detect a quantityof radiation reflected from the mirror.
 32. The system of claim 23,comprising: a reaction chamber to receive the pressurized gas sample anda second gas sample to produce an excited state of a third gas sample;and light-detecting device to detect a quantity of light emitted withina period of time during which the excited third gas sample returns to aground state from the excited state.